This type of toilet is sometimes called an "ecosan toilet", but ecological sanitation is a much broader concept, in which the nutrients present in human excrement are hygienically returned to agricultural soil, to produce food again.

Composting toilets with urine separation are similar to IESSO in that urine is isolated from feces, but they promote composting of feces instead of dehydration. However, this is more a matter of a gradient than a dichotomy, depending on climate, secant material, and other details.

The IESSO are especially applicable in the following situations:[2]​.

IESSOs can be built for schools and many already exist in Kenya, Rwanda and Uganda. These suffer from the same weaknesses as any other type of school toilet: if responsibilities are not clear and a budget is not dedicated to maintenance, they will go into decline.[3]​.

Basics

Urine separation takes advantage of the fact that the human body expels urine forward and feces backward. In a UDDT, urine drains through a depression or funnel at the front, while stool falls directly through another hole. This 'separation at the source' does not require the user to reposition themselves between the moments of urinating and defecating, although it is necessary to position themselves correctly on the user interface. After sending a defined stream forward, women may drip a little urine into the stool section. This is a small amount and does not affect normal operation.

Urine separation can also be achieved through the Coandă Effect, in which liquids are often guided by solids. In this case, the urine hits the surface of the toilet and follows it until it is channeled into a slot or tube, generally out of sight of the user.[4]​.

Designers and users of IESSOs must try to keep the accumulation of feces as dry as possible, to avoid the generation of odors or flies. It is worth mentioning that flies are not attracted to feces once they are dry. During storage, the natural moisture of the feces gradually evaporates and exits through the ventilation system. Much of the moisture is also absorbed into the material that covers the stool.

An IESSO consists of eight basic elements:[2]​.

The degree of dehydration achieved over time depends on local climatic conditions and the effectiveness of ventilation. In general, it is recommended to save feces for at least six months from the last intake of fresh feces.[2]​.

During this process, microbes break down the organic material. Pathogens in feces are eliminated with longer time, lower humidity, more extreme pH, greater diversity of microbes and greater presence of oxygen

https://www.inti.gob.ar/tecno\_sustentables/pdf/banosSecos.pdf

. One of the main objectives is to dehydrate the material beyond what pathogens, including helminths, can resist.

Fresh feces are about 80% water and most of it evaporates if not in airtight containers or chambers. Within six months, the humidity is generally reduced to less than 25%.[2] Depending on the degree of dryness and the intended use (for example, to fertilize the bottom of holes for planting trees or, on the other hand, for growing lettuce), additional treatment, such as composting or exposure to the sun in thin layers, may be necessary.

benches to sit

For seated use, it is advantageous to build benches integrated into the privacy wall, rather than pedestals that resemble conventional flush toilets. The Rotary Company of Peru has so far built more than 800 such toilets, in and near Lima, Peru.[5] This bench extends from wall to wall, above the feces accumulation chamber(s). A prefabricated contour or other funnel is placed to receive urine separately. Allows many more options for ventilation.

This type of toilet is beneficial for disabled users, compared to the pedestal model. The wide bench provides space for a helper (if necessary), the person can support themselves with their hands and there are more options for the location of handrails. More importantly for this audience, the benches reduce the need for steps or ramps.[6]​.

Accessibility

UDDTs are sometimes built with narrow steps with or without handrails, making access difficult for people with disabilities, but this should be avoided. The bench model, which was already mentioned, helps build with fewer steps and ramps.

When constructing a squat toilet, it is advisable to include a handle that users can grasp for balance.[6]​ For people with physical limitations when squatting, it is feasible to assemble a small portable bench to allow these people to sit on top of a squat toilet and, when not in use, be turned on its side.

Designs for flood zones

In locations susceptible to flooding, feces chambers should generally be above the maximum water level. Another option is to build with ferrocement walls that are joined with a waterproof floor.

Sources of components

IESSOs can be commercially manufactured in plastic, ceramic or fiberglass. On the other hand, they can be built locally with cement or other materials by users, local companies, NGOs or contractors. There is also the commercial sale of self-contained plastic units, with or without electric fans.

Waterless urinals

Many times, a waterless urinal is installed next to an IESSO, for the convenience of men who prefer to urinate standing up. This reduces the amount of urine that mixes with feces by mistake and, therefore, odors. UDDTs are designed to be used only while sitting or squatting. The urinal also allows urine to be collected in a purer manner, without the risk of fecal contamination. There are devices for female urination") that allow women to use male urinals, but it is preferable to assemble female urinals") for squatting or crouching positions, which is feasible with conventional funnels of about 25 cm in diameter.

Sitting or squatting

IESSOs are generally constructed for either sitting or squatting, depending on the users' preferences, although a few models allow both positions for defecation. For hygiene reasons, many people prefer squatting in public places, even if they choose to sit in their own homes. The squatting position also promotes colon health.[7]​.

Multi-story urban buildings

It is feasible to build tall buildings with IESSO, by installing combined ducts for ventilation and collection of feces and other pipes for urine. However, so far there is only one successful example, in the Gebers Housing Cooperative in Orhem, Sweden.[8]​.

A much larger-scale installation highlights the need to maintain building standards occurred in a project called the "Erdos Ecological City" in northern China.[9]​[10]​[11]​ The project was implemented from 2003 to 2009. This urban facility for 3,000 residents in multi-story buildings had IESSO and ducts for fecal collection in the basements. Other pipes carried urine and, separately, ventilation. There was also gray water treatment and composting of solid organic waste, for the reuse of these materials as irrigation and fertilizer in agriculture.

However, there were several design and implementation problems, the lack of a plan to address these deficiencies and corresponding complaints from residents, these IESSOs were replaced with conventional flushing toilets in 2009. The main factors driving this change were:[10]​.

If we take these lessons into account, future large-scale urban installations can be successful.[10]​.

a camera

It is a single space where one and another container is placed where feces accumulate. Depending on the size of the vault, two or more containers may be stored there, but only one would receive the fresh feces. The containers should not be larger than about 50 liters, so that they can be moved manually when filled. Once full, it is stored for dehydration or taken for treatment elsewhere. It is necessary to remove it carefully due to the presence of fresh feces. Optimally, containers should be permeable, to allow water evaporation and oxygen infiltration, as is the case with woven polypropylene bags, which are extremely accessible, economical and strong, those that come with rice, flour, etc. A plastic bucket does not allow as much ventilation, should not be stored tightly covered, and the contents may require additional treatment to control pathogens.[12]​ This treatment could include applying high temperatures, composting, or exposing them to sunlight in thin layers.

If the container is permeable and allows gas exchange, dehydration of feces is similar or better than in two-chamber IESSOs.[13]​.

two cameras

These have two tanks for feces, which are used alternately, allowing them to dry where they fall. While one is filling, the other dries for at least six months.[2] During this rest period, no new feces should enter that chamber and it is advisable to cover the hole that is not in use, so that confused users cannot use it. When the second chamber is full and at least 6 months have passed, the first is emptied with a shovel and the user interface is changed accordingly. Chambers are generally sized to fill in 6 to 12 months.[2]​.

Portable models

There are models that are essentially variations of the single-chamber type that are more portable and self-contained, including ones that users can assemble themselves. It usually depends on treatment of the stool elsewhere.

They are generally so compact and lightweight that one person can carry them. Its installation is generally simple, although some models use electricity to operate their fans that draw odors outside the building. It is common to use them on boats, motor homes and 'tiny houses'.

Mobile IESSOs usually include:

Some models have several of the following aspects:.

During normal use, an IESSO is as hygienic and safe as any other type of toilet. However, it is necessary to think about hygiene when removing or emptying feces and urine containers, although the risk is much lower than when emptying pit latrines or septic tanks. In the event that the feces remain in the same chamber or container longer than the time necessary for the pathogens to die, this risk is minimal. Toilet water is much riskier when it becomes clogged or when it flows into rivers, aquifers or seas without proper treatment.

Compared to a water toilet that is flushed without covering it, an IESSO has a lower risk of pathogens, such as Clostridium difficile, which are dispersed through aerosolization produced by the turbulence of the water. (http://ag.arizona.edu/media/archives/6.11.html)[14]​.

Regarding the health risks associated with reuse activities, the 2006 World Health Organization document entitled "Guidelines for the safe use of wastewater, excrement and gray water in agriculture" explains ways to minimize the risks.[15] The key concept is the application of the multi-barrier approach), which can also be applied in the use of materials produced in IESSOs.

Dry materials for anal cleansing

It is possible to clean yourself with toilet paper, leaves, corn gophers or even sticks and stones. They are deposited together with feces, where they decompose. For example, in South America the soft, scented leaves of Piper auritum and other species of the Piperaceae family, along with the Melastomataceae, are especially suitable for this function.[13]​ Some use stones, only they do not decompose and the space is filled sooner.

Used toilet paper can be stored in a bin and then burned, composted or buried, although this represents more work and new health risks. This applies mainly to portable units, for space reasons.

Anal cleansing with water

It is feasible to set up dry toilets for users who wash their anuses with water instead of using toilet paper. On squat models, an additional hole is added at the back to receive this water (as seen on the light blue model in the Design Considerations section). In seated models, another seat can be installed next to it for this cleaning. These adjustments are key, since you do not want to contaminate the urine or make the feces more moist.

Since it contains faeces, this cleaning water should be considered sewage and treated accordingly, for example by infiltration into the soil (well above the water table) or different types of phytoremediation.

Some users wash their anuses above the urine space. This simplifies construction, but contaminates the urine and requires further treatment or distribution about 20 cm below the soil surface using perforated hoses between fruit trees or other cultivated plants.

The water for this cleaning can be supplied through a hose or a jug or bottle that the user carries with them. It may be from rainwater collected from the roof.

Materials to cover stools

In most IESSO models, the same user must add a cup of some dry substance to cover the feces immediately after depositing it, to control odors, prevent flies from laying their eggs, visually cover them and absorb some of their moisture. It is also important that this material allows sufficient airflow for drying the stool, so it is desirable that the material contain some percentage of fibrous things that do not break down quickly. A variety of materials can be used, depending on what is available on site:

Lime and wood ash have the advantage of being alkaline and, by increasing the pH of the feces pile, they accelerate the death of pathogenic microbes.

It is beneficial to cover the feces with a material that also inoculates it with soil microbes that help break down and eliminate pathogens in the feces efficiently. Dried, decomposed fecal material from a previous cycle serves this function, after judicious treatment or storage. In addition, the user can add it with a cup, instead of touching it with their hands and, if in doubt, they would be encouraged to wash their hands well.[16]​[13]​.

In some cases, it is not necessary to cover the stool, especially when there is electric ventilation and a lid to prevent the stool from being seen when the user is not depositing it, as in some models from the Separett company. There are also public toilets where it is preferred that the caregiver add the material to cover the faeces, as users may not aim correctly or use incorrect amounts. The NGO Sanergy applies this system in poor neighborhoods in Kenya.

dry stools

The degree of further treatment required depends on the length of time it has stood and the intended use. If it is going to be used in agriculture, the elimination of possible pathogens must be ensured more carefully than if it is going to be placed in the bottoms of holes for planting trees. It is also necessary to apply more care in large public systems than in the case where the farmers' own product is applied to their own crops.

Secondary treatment may include:.

-- thermophilic composting, in which the temperature is above 50 °C for at least one week;.

-- additional storage (e.g. for more than one year);

-- treatment with ammonia from urine;

-- spread the material in thin layers in the sun, to receive ultraviolet rays;

-- high temperatures (for example, a solar oven that has temperatures greater than 65 °C for at least one hour).

The most difficult pathogens to eliminate from feces are helminth eggs, which we can look for with a microscope to evaluate the effectiveness of the treatment.

Treated in this way, the feces constitute a great amendment for the soil, with a high content of nitrogen, phosphorus, potassium and organic carbon. If you do not want to take advantage of this resource and do these treatments, it is feasible to bury it under at least 25 cm of soil to protect public health.[2]​.

Urine

Urine does not transmit diseases when dispersed on the ground, but may receive some fecal contamination from users who do not use the IESSO correctly. The required degree of treatment depends on the use to which it is put. If it is dispersed in buried perforated hoses, under 10 or 20 cm of soil planted with plants, these are fertilized without risk. If you do not want to take advantage of this resource, it can infiltrate the soil, without treatment, at safe distances from the water table or water wells.

When it comes out of a healthy person, urine is almost sterile and requires much less treatment than feces to eliminate possible pathogens. The few that are transmitted through urine are: Leptospira interrogans, salmonella, Salmonella paratyphi, Schistosoma haematobium, BK virus, Papovirus SV-40.[17]​[18]​[19]​ and the Ebola virus. The exact survival time of these organisms in urine (outside the body) or in soil has not yet been determined.

It is not necessary to treat urine if it is applied to crops for self-consumption of the same family, since there is a greater risk of transmitting diseases between family members through hugs, kisses, shaking hands and the use of the same kitchen and the same toilet.

The simplest and most common way to eliminate pathogens from urine is to store it in airtight containers. The decomposition of urea gives rise to ammonia, which increases the pH to values ​​greater than 9. In general, pathogens cannot resist ammonia or this pH and this process is more efficient in warm climates and when urine is not diluted.[2]​.

Urine storage kills possible pathogenic bacteria present, such as Salmonella typhi and paratyphi and Mycobacterium tuberculosis, in a relatively short time: five weeks at temperatures below 20 °C or two weeks at higher temperatures.

For greater safety against possible pathogens, it is recommended to store urine for one to six months, depending on environmental temperatures, the size of the system and the types of crops to be fertilized.

Urine is a great fertilizer for plants, thanks to its content of nitrogen, phosphorus, potassium and organic carbon. Generally it must be diluted, being careful not to overdose the plants, although it can be applied pure and in larger quantities to the soil, more than a week before sowing. Another way to fertilize with urine is to disperse it on the ground, among cultivated plants or trees, using buried perforated hoses. Clogging of the hoses is avoided by not using Ts or unions and by placing plastic meshes in the urine funnels.

In cases where you do not want to use urine, it is feasible to infiltrate it into holes in the ground, unless it would contaminate someone's water sources. For example, in the municipality of eThekwini in South Africa and in Lima, Peru, urine infiltrates into the soil, without problems, since the groundwater is very deep and no one consumes it.

pit latrines

The following advantages favor UDDT over pit latrines:[2]​.

The NGO WECF introduced IESSO to countries in Eastern Europe and Central Asia, where people had pit latrines. It was very successful among people in regions that do not have reliable piped water and wastewater purification systems. Since a change in user behavior is required, awareness and training were very important.

Water drag systems

It is more complicated to compare UDDTs with sewer-based systems and wastewater treatment plants, since sewers not only transport excrement, but also gray water, runoff, and industrial wastewater. Additionally, the costs of building and operating this aquatic infrastructure are enormous, and the more people use UDDTs, the lower these costs will be.

In many places, it is not feasible to build sewage and WWTPs due to high costs and water scarcity. Furthermore, unlike IESSOs, water toilets dilute excrement and create colossal waste streams. The economic advantages of UDDTs are even greater in the case of portable models that can be quickly installed at low cost.

In IESSOs, the collection of urine and feces separately, without the use of water, prevents the entry of hormones, drugs and other chemicals into rivers, aquifers and seas. Conventional WWTPs cannot completely remove these substances, which are now found in concentrations of around 50 ng/L in groundwater at some locations in Germany.[20]​[21]​.

What's more, these micropollutants tend to concentrate in the sludge generated in WWTPs.[22]​ After treatment, these sludge are buried in landfills, incinerated, applied to agricultural soils, given away or sold to the public.[23]​[24]​ Each of these options implies risks for public and environmental health.[25]​[26]​ By not mixing human excrement with the contaminants that are discarded in sewers or septic tanks, IESSOs produce much better quality fertilizers.

If the excrement collected in IESSOs receives additional treatment, is buried, or is integrated into the soil, drug residues will be destroyed more safely than in aquatic systems. Therefore, IESSOs and other urine-separating toilets have great advantages over water toilets in controlling micropollutants.

Operational issues

Problems that may arise in the management of IESSO include the following:[2]​.

• Obstruction of the tubes that carry urine. It is important to select these tubes well and install them properly. It is advisable to place a plastic mesh in the funnel that receives the urine, to prevent the entry of solids.

• Bad odors from the feces chamber. This is due to excess moisture, urine ingress, the addition of insufficient drying material, or both. It is necessary to raise awareness and educate users about the correct handling of the system.

• Ammonia smell. Urine should not collect in any part of the pipes, since it would ferment there and produce this bad smell, therefore, these pipes must be installed correctly. If urine accumulates in containers, it is key to change these in time and avoid urine spillage.

• Presence of flies or rodents. To control this, it is important to cover the feces with adequate amounts (usually one cup) of drying material, especially soil, compost or dried, decomposed feces from a previous cycle (or these mixed in other materials). It is also advisable to kill these animals with traps and possibly improve ventilation to prevent the entry of flies.

• Using the wrong camera in two-chamber UDDT. The passive deposit must be covered in a way that avoids or makes this confusion impossible and user education is always key.

These problems are easy to solve through proper construction, education and monitoring. However, users or caregivers have to be committed and willing. Otherwise, it may lead to the abandonment of these toilets.

Awareness and coordination

IESSO users should be more aware of the importance of correct use, for example preventing urine from entering the stool area, stocking up on drying material and changing containers. Users of flush toilets, on the other hand, only have to remember to flush, brush and unclog clogs, but they waste and contaminate large amounts of water and, in many cases, dirty their own environment.[9]​.

IESSOs are sometimes considered too expensive compared to pit latrines, but this criticism does not include the cost of emptying the pits, nor the value of fertilizers that can be recycled through IESSOs. Not only the construction costs but also the long-term costs and benefits must be taken into account, especially since the costs of emptying and rebuilding the pits can be considerable.[27] When considering a 10-year period, UDDT can be much more economical, since emptying is much easier and safer, therefore less expensive, even if users hire someone else to do it.

Compared to flush toilets, sewers and wastewater treatment plants, IESSOs are much less expensive. However, it must be remembered that this system also receives gray water and other waste so it cannot be compared directly. This calculation has been carried out for the case of Lima, Peru.[28]​.

There is even a minimalist model that effectively costs nothing to build and only requires rescuing and assembling a few plastic objects selected from the trash, so that the poorest people, victims of disasters and those who simply want to gain experience with the IESSO, without investing funds, can do so.[12]​.

Although some ancient cultures may have made IESSO, the first modern models with two chambers were designed in Japan, around 1950, and later developed in Vietnam, as a way to increase the safety of the use of human excrement in agriculture.[29]​ In this way, its development was closely linked to ecological sanitation (EcoSan), in which nutrients and organic matter are recycled in agriculture. Since around 2000, they have been promoted for their various advantages, even if you don't want to take advantage of fertilizers.

Since the 1990s, modifications to the design have been developed, such as tubes to vent the stool chambers. Prefabricated UDDTs in ceramic, plastic and fiberglass were launched on the market, thus increasing the durability and elegance of the system.

These toilets have been produced commercially in Sweden since the mid-1990s. Between 1994 and 2010, the Separett company sold about 200,000. Many are available for sale and are used in places where it is not possible, permitted or desirable to connect to the sewer, for example in cabins in the woods or camping sites. Since the beginning, there have always also been users who build for themselves with easily accessible materials.

South Africa (eThekwini Municipality, Durban)

This municipality has installed the largest group of IESSO in the world. As of 2015, they had about 80,000 units serving about 500,000 residents. Currently they do not use fertilizers).

Colombia

Recently and with the trend of tiny house homes, eco-friendly dry toilets are being implemented in this type of units that can be mobile or fixed. For now (2021), versions of dry toilets produced by the company LEHO SAS are in the pilot and demonstration phase, which include internal visual barrier mechanisms and a cover material dispenser. These toilets have been designed adapting to the standards of use of traditional toilets, with familiar actions for users new to these technologies, which is expected to facilitate their adoption as comfortable, dignified and effective solutions.

Haiti

The NGO SOIL[30]​ in Haiti began building IESSO and composting stations for feces in Port-au-Prince, as part of humanitarian aid after the 2010 Earthquake in northern Haiti.[31]​ They then diversified by offering toilets for residential homes, with the aim of gradually shifting from humanitarian aid to the sustainable provision of an Ecological Sanitation service for paying clients. Its current design consists of portable units with a single chamber where a bucket is placed to receive feces. The vast majority have a funnel to separate urine. In 2014, they converted all of their two-chamber public use units to single-chamber operation with interchangeable plastic barrels to receive feces. This allows them to serve an unlimited number of people and facilitates the process of transferring the material to their composting facilities, so their entire operation works based on containers.[32]​ This allows them to serve many people and ensure that the final product is safe to apply to the soil. In most of the toilets this organization installs, it gets rid of urine by simply letting it infiltrate the floor.

SOIL continues to provide humanitarian aid in some of Haiti's most vulnerable communities, especially those hardest hit by the cholera epidemic, by offering free access to its dry toilets to more than 3,500 people. In addition, more than 2,000 people use its services through its pilot business project "EkoLakay", which has an increasingly long waiting list, demonstrating the existence of market demand for economic sanitation, even in communities that are extremely poor.

After building its first composting facility in Haiti in 2009, SOIL has become one of the largest waste treatment operations in the country. Currently, its two facilities convert more than 76,000 liters of human feces into safe, organic, agricultural-grade compost each month. They sell it to farmers, organizations, companies and institutions in different parts of the country, to help finance this operation.

Ecuador

So far, hundreds of IESSOs have been built. Various models adjust to different preferences, budgets, conditions and, sometimes, the need to transport materials to distant places in the Amazon jungle that are only accessible by light aircraft.[13]​.

Many of these serve indigenous communities and ecotourism operations in the Amazon part of the country. In these places, there is generally no piped water and the clay soils, together with high groundwater levels, do not allow sewage to infiltrate the soil. These factors make the application of other excrement management systems difficult. For example, governments and tourism operations frequently install water toilets that flow directly into rivers or into holes in the ground, where they cannot infiltrate, due to soil conditions. With abundant rains, these holes fill and overflow into the rivers. Many of the communities live along small streams that can easily become contaminated due to low dilution, constituting a danger to those who swim, fish, wash clothes or drink the water in these rivers.

Namibia

In Namibia, a type of IESSO called the "Otji Toilet" has been developed, which takes advantage of the Coandă Effect to separate most of the urine through a slot at the base of its pedestal, where it is directed to an infiltration hole. Between 2003 and 2011, some 1,200 Otji Toilets have been installed in southern Namibia and in the rural area around Otjiwarongo. With the same design, the NGO EcoSur has built dry toilets in Ecuador and El Salvador since 2007.[33]​.

Use on boats, RVs and camping

• For sailors, it is very convenient to replace nautical toilets, which store sewage or discharge it directly, to IESSO. There are models that were designed specifically for boats and RVs, such as the "C-Head", "BoonJon", "Nature's Head" and "Air Head" brands.

• In camping, the idea of ​​"leave no trace" is not only a philosophy, but a necessity in areas where human excrement cannot decompose naturally. There are now lightweight models from IESSO that allow feces to be packed and removed from natural areas (for example, one from the Swedish company Separett). Only urine is left behind, which is of much less concern, since it contains almost no pathogens.

Barriers to acceptance

There are some barriers to universal acceptance of this technology and the importance of these varies between different parts of the world: lack of awareness regarding water pollution, little knowledge about the value of human excrement as fertilizer, difficult access to prefabricated components of IESSO and little financing for decentralized sanitation.[2] The existing extensive networks of piped water and sewage may also represent impediments to the adoption of UDDT, since they eliminate two of the factors that drive them and, in addition, represent large public investments. They may restrict efforts to change types of toilets and sanitation.

Another big impediment is that no one wants to handle human excrement. Therefore, it is important to design and promote models that minimize observation, smell and contact with this material during maintenance activities. It is also a reason to organize private or municipal operations for the collection, transportation and treatment of excrement. They could operate similarly to kitchen and garden organic waste collection programs.

It is important that the sanitation system that is selected conforms to the legal framework and that it receives support from the local government.[9]​.

Policies could encourage the extensive use of IESSO through financial support of research programs, regulations requiring resource recovery from wastewater, and strict compliance with standards that control environmental pollution.[9]​.

Number of users

Although there are no exact figures, the German Development Cooperation Agency (GIZ) has estimated, in 2012, that there are about 2 million IESSO users, based on known projects in 84 countries.

Regulations

The International Association of Plumbing and Mechanical Officials (IAPMO) has recently proposed an addendum to its Green Plumbing Code, which “indicates performance criteria for mass-produced or site-built composting toilets, with or without urine separation.”[34] If approved, it will appear in the 2015 edition of the Green Supplement to the Uniform Plumbing Code.

Several North American states allow the disposal of feces from IESSO or composting toilets (generally, they do not distinguish between dry toilet types) by burying them under at least 6 inches of soil. For example:.

For dry toilet users in the United States (including those using IESSO), it is important to remember that while it does not refer to this material as “fertilizer,” but simply a disposable material, Federal Rule 503 (called the “EPA Sludge Rule”) has no jurisdiction over dry toilet products and all control of these materials rests with individual states.[39]​.

Currently, the use of urine as fertilizer in the US is still in its infancy. The NGO Rich Earth Institute (richearhinstitute.org) is demonstrating its feasibility in Brattleboro, Vermont. So far, there do not appear to be regulations specifically regarding urine use in the US, but as urine-separating toilets become more common, they need to be formulated.

This type of toilet is sometimes called an "ecosan toilet", but ecological sanitation is a much broader concept, in which the nutrients present in human excrement are hygienically returned to agricultural soil, to produce food again.

Composting toilets with urine separation are similar to IESSO in that urine is isolated from feces, but they promote composting of feces instead of dehydration. However, this is more a matter of a gradient than a dichotomy, depending on climate, secant material, and other details.

The IESSO are especially applicable in the following situations:[2]​.

IESSOs can be built for schools and many already exist in Kenya, Rwanda and Uganda. These suffer from the same weaknesses as any other type of school toilet: if responsibilities are not clear and a budget is not dedicated to maintenance, they will go into decline.[3]​.

Basics

Urine separation takes advantage of the fact that the human body expels urine forward and feces backward. In a UDDT, urine drains through a depression or funnel at the front, while stool falls directly through another hole. This 'separation at the source' does not require the user to reposition themselves between the moments of urinating and defecating, although it is necessary to position themselves correctly on the user interface. After sending a defined stream forward, women may drip a little urine into the stool section. This is a small amount and does not affect normal operation.

Urine separation can also be achieved through the Coandă Effect, in which liquids are often guided by solids. In this case, the urine hits the surface of the toilet and follows it until it is channeled into a slot or tube, generally out of sight of the user.[4]​.

Designers and users of IESSOs must try to keep the accumulation of feces as dry as possible, to avoid the generation of odors or flies. It is worth mentioning that flies are not attracted to feces once they are dry. During storage, the natural moisture of the feces gradually evaporates and exits through the ventilation system. Much of the moisture is also absorbed into the material that covers the stool.

An IESSO consists of eight basic elements:[2]​.

The degree of dehydration achieved over time depends on local climatic conditions and the effectiveness of ventilation. In general, it is recommended to save feces for at least six months from the last intake of fresh feces.[2]​.

During this process, microbes break down the organic material. Pathogens in feces are eliminated with longer time, lower humidity, more extreme pH, greater diversity of microbes and greater presence of oxygen

https://www.inti.gob.ar/tecno\_sustentables/pdf/banosSecos.pdf

. One of the main objectives is to dehydrate the material beyond what pathogens, including helminths, can resist.

Fresh feces are about 80% water and most of it evaporates if not in airtight containers or chambers. Within six months, the humidity is generally reduced to less than 25%.[2] Depending on the degree of dryness and the intended use (for example, to fertilize the bottom of holes for planting trees or, on the other hand, for growing lettuce), additional treatment, such as composting or exposure to the sun in thin layers, may be necessary.

benches to sit

For seated use, it is advantageous to build benches integrated into the privacy wall, rather than pedestals that resemble conventional flush toilets. The Rotary Company of Peru has so far built more than 800 such toilets, in and near Lima, Peru.[5] This bench extends from wall to wall, above the feces accumulation chamber(s). A prefabricated contour or other funnel is placed to receive urine separately. Allows many more options for ventilation.

This type of toilet is beneficial for disabled users, compared to the pedestal model. The wide bench provides space for a helper (if necessary), the person can support themselves with their hands and there are more options for the location of handrails. More importantly for this audience, the benches reduce the need for steps or ramps.[6]​.

Accessibility

UDDTs are sometimes built with narrow steps with or without handrails, making access difficult for people with disabilities, but this should be avoided. The bench model, which was already mentioned, helps build with fewer steps and ramps.

When constructing a squat toilet, it is advisable to include a handle that users can grasp for balance.[6]​ For people with physical limitations when squatting, it is feasible to assemble a small portable bench to allow these people to sit on top of a squat toilet and, when not in use, be turned on its side.

Designs for flood zones

In locations susceptible to flooding, feces chambers should generally be above the maximum water level. Another option is to build with ferrocement walls that are joined with a waterproof floor.

Sources of components

IESSOs can be commercially manufactured in plastic, ceramic or fiberglass. On the other hand, they can be built locally with cement or other materials by users, local companies, NGOs or contractors. There is also the commercial sale of self-contained plastic units, with or without electric fans.

Waterless urinals

Many times, a waterless urinal is installed next to an IESSO, for the convenience of men who prefer to urinate standing up. This reduces the amount of urine that mixes with feces by mistake and, therefore, odors. UDDTs are designed to be used only while sitting or squatting. The urinal also allows urine to be collected in a purer manner, without the risk of fecal contamination. There are devices for female urination") that allow women to use male urinals, but it is preferable to assemble female urinals") for squatting or crouching positions, which is feasible with conventional funnels of about 25 cm in diameter.

Sitting or squatting

IESSOs are generally constructed for either sitting or squatting, depending on the users' preferences, although a few models allow both positions for defecation. For hygiene reasons, many people prefer squatting in public places, even if they choose to sit in their own homes. The squatting position also promotes colon health.[7]​.

Multi-story urban buildings

It is feasible to build tall buildings with IESSO, by installing combined ducts for ventilation and collection of feces and other pipes for urine. However, so far there is only one successful example, in the Gebers Housing Cooperative in Orhem, Sweden.[8]​.

A much larger-scale installation highlights the need to maintain building standards occurred in a project called the "Erdos Ecological City" in northern China.[9]​[10]​[11]​ The project was implemented from 2003 to 2009. This urban facility for 3,000 residents in multi-story buildings had IESSO and ducts for fecal collection in the basements. Other pipes carried urine and, separately, ventilation. There was also gray water treatment and composting of solid organic waste, for the reuse of these materials as irrigation and fertilizer in agriculture.

However, there were several design and implementation problems, the lack of a plan to address these deficiencies and corresponding complaints from residents, these IESSOs were replaced with conventional flushing toilets in 2009. The main factors driving this change were:[10]​.

If we take these lessons into account, future large-scale urban installations can be successful.[10]​.

a camera

It is a single space where one and another container is placed where feces accumulate. Depending on the size of the vault, two or more containers may be stored there, but only one would receive the fresh feces. The containers should not be larger than about 50 liters, so that they can be moved manually when filled. Once full, it is stored for dehydration or taken for treatment elsewhere. It is necessary to remove it carefully due to the presence of fresh feces. Optimally, containers should be permeable, to allow water evaporation and oxygen infiltration, as is the case with woven polypropylene bags, which are extremely accessible, economical and strong, those that come with rice, flour, etc. A plastic bucket does not allow as much ventilation, should not be stored tightly covered, and the contents may require additional treatment to control pathogens.[12]​ This treatment could include applying high temperatures, composting, or exposing them to sunlight in thin layers.

If the container is permeable and allows gas exchange, dehydration of feces is similar or better than in two-chamber IESSOs.[13]​.

two cameras

These have two tanks for feces, which are used alternately, allowing them to dry where they fall. While one is filling, the other dries for at least six months.[2] During this rest period, no new feces should enter that chamber and it is advisable to cover the hole that is not in use, so that confused users cannot use it. When the second chamber is full and at least 6 months have passed, the first is emptied with a shovel and the user interface is changed accordingly. Chambers are generally sized to fill in 6 to 12 months.[2]​.

Portable models

There are models that are essentially variations of the single-chamber type that are more portable and self-contained, including ones that users can assemble themselves. It usually depends on treatment of the stool elsewhere.

They are generally so compact and lightweight that one person can carry them. Its installation is generally simple, although some models use electricity to operate their fans that draw odors outside the building. It is common to use them on boats, motor homes and 'tiny houses'.

Mobile IESSOs usually include:

Some models have several of the following aspects:.

During normal use, an IESSO is as hygienic and safe as any other type of toilet. However, it is necessary to think about hygiene when removing or emptying feces and urine containers, although the risk is much lower than when emptying pit latrines or septic tanks. In the event that the feces remain in the same chamber or container longer than the time necessary for the pathogens to die, this risk is minimal. Toilet water is much riskier when it becomes clogged or when it flows into rivers, aquifers or seas without proper treatment.

Compared to a water toilet that is flushed without covering it, an IESSO has a lower risk of pathogens, such as Clostridium difficile, which are dispersed through aerosolization produced by the turbulence of the water. (http://ag.arizona.edu/media/archives/6.11.html)[14]​.

Regarding the health risks associated with reuse activities, the 2006 World Health Organization document entitled "Guidelines for the safe use of wastewater, excrement and gray water in agriculture" explains ways to minimize the risks.[15] The key concept is the application of the multi-barrier approach), which can also be applied in the use of materials produced in IESSOs.

Dry materials for anal cleansing

It is possible to clean yourself with toilet paper, leaves, corn gophers or even sticks and stones. They are deposited together with feces, where they decompose. For example, in South America the soft, scented leaves of Piper auritum and other species of the Piperaceae family, along with the Melastomataceae, are especially suitable for this function.[13]​ Some use stones, only they do not decompose and the space is filled sooner.

Used toilet paper can be stored in a bin and then burned, composted or buried, although this represents more work and new health risks. This applies mainly to portable units, for space reasons.

Anal cleansing with water

It is feasible to set up dry toilets for users who wash their anuses with water instead of using toilet paper. On squat models, an additional hole is added at the back to receive this water (as seen on the light blue model in the Design Considerations section). In seated models, another seat can be installed next to it for this cleaning. These adjustments are key, since you do not want to contaminate the urine or make the feces more moist.

Since it contains faeces, this cleaning water should be considered sewage and treated accordingly, for example by infiltration into the soil (well above the water table) or different types of phytoremediation.

Some users wash their anuses above the urine space. This simplifies construction, but contaminates the urine and requires further treatment or distribution about 20 cm below the soil surface using perforated hoses between fruit trees or other cultivated plants.

The water for this cleaning can be supplied through a hose or a jug or bottle that the user carries with them. It may be from rainwater collected from the roof.

Materials to cover stools

In most IESSO models, the same user must add a cup of some dry substance to cover the feces immediately after depositing it, to control odors, prevent flies from laying their eggs, visually cover them and absorb some of their moisture. It is also important that this material allows sufficient airflow for drying the stool, so it is desirable that the material contain some percentage of fibrous things that do not break down quickly. A variety of materials can be used, depending on what is available on site:

Lime and wood ash have the advantage of being alkaline and, by increasing the pH of the feces pile, they accelerate the death of pathogenic microbes.

It is beneficial to cover the feces with a material that also inoculates it with soil microbes that help break down and eliminate pathogens in the feces efficiently. Dried, decomposed fecal material from a previous cycle serves this function, after judicious treatment or storage. In addition, the user can add it with a cup, instead of touching it with their hands and, if in doubt, they would be encouraged to wash their hands well.[16]​[13]​.

In some cases, it is not necessary to cover the stool, especially when there is electric ventilation and a lid to prevent the stool from being seen when the user is not depositing it, as in some models from the Separett company. There are also public toilets where it is preferred that the caregiver add the material to cover the faeces, as users may not aim correctly or use incorrect amounts. The NGO Sanergy applies this system in poor neighborhoods in Kenya.

dry stools

The degree of further treatment required depends on the length of time it has stood and the intended use. If it is going to be used in agriculture, the elimination of possible pathogens must be ensured more carefully than if it is going to be placed in the bottoms of holes for planting trees. It is also necessary to apply more care in large public systems than in the case where the farmers' own product is applied to their own crops.

Secondary treatment may include:.

-- thermophilic composting, in which the temperature is above 50 °C for at least one week;.

-- additional storage (e.g. for more than one year);

-- treatment with ammonia from urine;

-- spread the material in thin layers in the sun, to receive ultraviolet rays;

-- high temperatures (for example, a solar oven that has temperatures greater than 65 °C for at least one hour).

The most difficult pathogens to eliminate from feces are helminth eggs, which we can look for with a microscope to evaluate the effectiveness of the treatment.

Treated in this way, the feces constitute a great amendment for the soil, with a high content of nitrogen, phosphorus, potassium and organic carbon. If you do not want to take advantage of this resource and do these treatments, it is feasible to bury it under at least 25 cm of soil to protect public health.[2]​.

Urine

Urine does not transmit diseases when dispersed on the ground, but may receive some fecal contamination from users who do not use the IESSO correctly. The required degree of treatment depends on the use to which it is put. If it is dispersed in buried perforated hoses, under 10 or 20 cm of soil planted with plants, these are fertilized without risk. If you do not want to take advantage of this resource, it can infiltrate the soil, without treatment, at safe distances from the water table or water wells.

When it comes out of a healthy person, urine is almost sterile and requires much less treatment than feces to eliminate possible pathogens. The few that are transmitted through urine are: Leptospira interrogans, salmonella, Salmonella paratyphi, Schistosoma haematobium, BK virus, Papovirus SV-40.[17]​[18]​[19]​ and the Ebola virus. The exact survival time of these organisms in urine (outside the body) or in soil has not yet been determined.

It is not necessary to treat urine if it is applied to crops for self-consumption of the same family, since there is a greater risk of transmitting diseases between family members through hugs, kisses, shaking hands and the use of the same kitchen and the same toilet.

The simplest and most common way to eliminate pathogens from urine is to store it in airtight containers. The decomposition of urea gives rise to ammonia, which increases the pH to values ​​greater than 9. In general, pathogens cannot resist ammonia or this pH and this process is more efficient in warm climates and when urine is not diluted.[2]​.

Urine storage kills possible pathogenic bacteria present, such as Salmonella typhi and paratyphi and Mycobacterium tuberculosis, in a relatively short time: five weeks at temperatures below 20 °C or two weeks at higher temperatures.

For greater safety against possible pathogens, it is recommended to store urine for one to six months, depending on environmental temperatures, the size of the system and the types of crops to be fertilized.

Urine is a great fertilizer for plants, thanks to its content of nitrogen, phosphorus, potassium and organic carbon. Generally it must be diluted, being careful not to overdose the plants, although it can be applied pure and in larger quantities to the soil, more than a week before sowing. Another way to fertilize with urine is to disperse it on the ground, among cultivated plants or trees, using buried perforated hoses. Clogging of the hoses is avoided by not using Ts or unions and by placing plastic meshes in the urine funnels.

In cases where you do not want to use urine, it is feasible to infiltrate it into holes in the ground, unless it would contaminate someone's water sources. For example, in the municipality of eThekwini in South Africa and in Lima, Peru, urine infiltrates into the soil, without problems, since the groundwater is very deep and no one consumes it.

pit latrines

The following advantages favor UDDT over pit latrines:[2]​.

The NGO WECF introduced IESSO to countries in Eastern Europe and Central Asia, where people had pit latrines. It was very successful among people in regions that do not have reliable piped water and wastewater purification systems. Since a change in user behavior is required, awareness and training were very important.

Water drag systems

It is more complicated to compare UDDTs with sewer-based systems and wastewater treatment plants, since sewers not only transport excrement, but also gray water, runoff, and industrial wastewater. Additionally, the costs of building and operating this aquatic infrastructure are enormous, and the more people use UDDTs, the lower these costs will be.

In many places, it is not feasible to build sewage and WWTPs due to high costs and water scarcity. Furthermore, unlike IESSOs, water toilets dilute excrement and create colossal waste streams. The economic advantages of UDDTs are even greater in the case of portable models that can be quickly installed at low cost.

In IESSOs, the collection of urine and feces separately, without the use of water, prevents the entry of hormones, drugs and other chemicals into rivers, aquifers and seas. Conventional WWTPs cannot completely remove these substances, which are now found in concentrations of around 50 ng/L in groundwater at some locations in Germany.[20]​[21]​.

What's more, these micropollutants tend to concentrate in the sludge generated in WWTPs.[22]​ After treatment, these sludge are buried in landfills, incinerated, applied to agricultural soils, given away or sold to the public.[23]​[24]​ Each of these options implies risks for public and environmental health.[25]​[26]​ By not mixing human excrement with the contaminants that are discarded in sewers or septic tanks, IESSOs produce much better quality fertilizers.

If the excrement collected in IESSOs receives additional treatment, is buried, or is integrated into the soil, drug residues will be destroyed more safely than in aquatic systems. Therefore, IESSOs and other urine-separating toilets have great advantages over water toilets in controlling micropollutants.

Operational issues

Problems that may arise in the management of IESSO include the following:[2]​.

• Obstruction of the tubes that carry urine. It is important to select these tubes well and install them properly. It is advisable to place a plastic mesh in the funnel that receives the urine, to prevent the entry of solids.

• Bad odors from the feces chamber. This is due to excess moisture, urine ingress, the addition of insufficient drying material, or both. It is necessary to raise awareness and educate users about the correct handling of the system.

• Ammonia smell. Urine should not collect in any part of the pipes, since it would ferment there and produce this bad smell, therefore, these pipes must be installed correctly. If urine accumulates in containers, it is key to change these in time and avoid urine spillage.

• Presence of flies or rodents. To control this, it is important to cover the feces with adequate amounts (usually one cup) of drying material, especially soil, compost or dried, decomposed feces from a previous cycle (or these mixed in other materials). It is also advisable to kill these animals with traps and possibly improve ventilation to prevent the entry of flies.

• Using the wrong camera in two-chamber UDDT. The passive deposit must be covered in a way that avoids or makes this confusion impossible and user education is always key.

These problems are easy to solve through proper construction, education and monitoring. However, users or caregivers have to be committed and willing. Otherwise, it may lead to the abandonment of these toilets.

Awareness and coordination

IESSO users should be more aware of the importance of correct use, for example preventing urine from entering the stool area, stocking up on drying material and changing containers. Users of flush toilets, on the other hand, only have to remember to flush, brush and unclog clogs, but they waste and contaminate large amounts of water and, in many cases, dirty their own environment.[9]​.

IESSOs are sometimes considered too expensive compared to pit latrines, but this criticism does not include the cost of emptying the pits, nor the value of fertilizers that can be recycled through IESSOs. Not only the construction costs but also the long-term costs and benefits must be taken into account, especially since the costs of emptying and rebuilding the pits can be considerable.[27] When considering a 10-year period, UDDT can be much more economical, since emptying is much easier and safer, therefore less expensive, even if users hire someone else to do it.

Compared to flush toilets, sewers and wastewater treatment plants, IESSOs are much less expensive. However, it must be remembered that this system also receives gray water and other waste so it cannot be compared directly. This calculation has been carried out for the case of Lima, Peru.[28]​.

There is even a minimalist model that effectively costs nothing to build and only requires rescuing and assembling a few plastic objects selected from the trash, so that the poorest people, victims of disasters and those who simply want to gain experience with the IESSO, without investing funds, can do so.[12]​.

Although some ancient cultures may have made IESSO, the first modern models with two chambers were designed in Japan, around 1950, and later developed in Vietnam, as a way to increase the safety of the use of human excrement in agriculture.[29]​ In this way, its development was closely linked to ecological sanitation (EcoSan), in which nutrients and organic matter are recycled in agriculture. Since around 2000, they have been promoted for their various advantages, even if you don't want to take advantage of fertilizers.

Since the 1990s, modifications to the design have been developed, such as tubes to vent the stool chambers. Prefabricated UDDTs in ceramic, plastic and fiberglass were launched on the market, thus increasing the durability and elegance of the system.

These toilets have been produced commercially in Sweden since the mid-1990s. Between 1994 and 2010, the Separett company sold about 200,000. Many are available for sale and are used in places where it is not possible, permitted or desirable to connect to the sewer, for example in cabins in the woods or camping sites. Since the beginning, there have always also been users who build for themselves with easily accessible materials.

South Africa (eThekwini Municipality, Durban)

This municipality has installed the largest group of IESSO in the world. As of 2015, they had about 80,000 units serving about 500,000 residents. Currently they do not use fertilizers).

Colombia

Recently and with the trend of tiny house homes, eco-friendly dry toilets are being implemented in this type of units that can be mobile or fixed. For now (2021), versions of dry toilets produced by the company LEHO SAS are in the pilot and demonstration phase, which include internal visual barrier mechanisms and a cover material dispenser. These toilets have been designed adapting to the standards of use of traditional toilets, with familiar actions for users new to these technologies, which is expected to facilitate their adoption as comfortable, dignified and effective solutions.

Haiti

The NGO SOIL[30]​ in Haiti began building IESSO and composting stations for feces in Port-au-Prince, as part of humanitarian aid after the 2010 Earthquake in northern Haiti.[31]​ They then diversified by offering toilets for residential homes, with the aim of gradually shifting from humanitarian aid to the sustainable provision of an Ecological Sanitation service for paying clients. Its current design consists of portable units with a single chamber where a bucket is placed to receive feces. The vast majority have a funnel to separate urine. In 2014, they converted all of their two-chamber public use units to single-chamber operation with interchangeable plastic barrels to receive feces. This allows them to serve an unlimited number of people and facilitates the process of transferring the material to their composting facilities, so their entire operation works based on containers.[32]​ This allows them to serve many people and ensure that the final product is safe to apply to the soil. In most of the toilets this organization installs, it gets rid of urine by simply letting it infiltrate the floor.

SOIL continues to provide humanitarian aid in some of Haiti's most vulnerable communities, especially those hardest hit by the cholera epidemic, by offering free access to its dry toilets to more than 3,500 people. In addition, more than 2,000 people use its services through its pilot business project "EkoLakay", which has an increasingly long waiting list, demonstrating the existence of market demand for economic sanitation, even in communities that are extremely poor.

After building its first composting facility in Haiti in 2009, SOIL has become one of the largest waste treatment operations in the country. Currently, its two facilities convert more than 76,000 liters of human feces into safe, organic, agricultural-grade compost each month. They sell it to farmers, organizations, companies and institutions in different parts of the country, to help finance this operation.

Ecuador

So far, hundreds of IESSOs have been built. Various models adjust to different preferences, budgets, conditions and, sometimes, the need to transport materials to distant places in the Amazon jungle that are only accessible by light aircraft.[13]​.

Many of these serve indigenous communities and ecotourism operations in the Amazon part of the country. In these places, there is generally no piped water and the clay soils, together with high groundwater levels, do not allow sewage to infiltrate the soil. These factors make the application of other excrement management systems difficult. For example, governments and tourism operations frequently install water toilets that flow directly into rivers or into holes in the ground, where they cannot infiltrate, due to soil conditions. With abundant rains, these holes fill and overflow into the rivers. Many of the communities live along small streams that can easily become contaminated due to low dilution, constituting a danger to those who swim, fish, wash clothes or drink the water in these rivers.

Namibia

In Namibia, a type of IESSO called the "Otji Toilet" has been developed, which takes advantage of the Coandă Effect to separate most of the urine through a slot at the base of its pedestal, where it is directed to an infiltration hole. Between 2003 and 2011, some 1,200 Otji Toilets have been installed in southern Namibia and in the rural area around Otjiwarongo. With the same design, the NGO EcoSur has built dry toilets in Ecuador and El Salvador since 2007.[33]​.

Use on boats, RVs and camping

• For sailors, it is very convenient to replace nautical toilets, which store sewage or discharge it directly, to IESSO. There are models that were designed specifically for boats and RVs, such as the "C-Head", "BoonJon", "Nature's Head" and "Air Head" brands.

• In camping, the idea of ​​"leave no trace" is not only a philosophy, but a necessity in areas where human excrement cannot decompose naturally. There are now lightweight models from IESSO that allow feces to be packed and removed from natural areas (for example, one from the Swedish company Separett). Only urine is left behind, which is of much less concern, since it contains almost no pathogens.

Barriers to acceptance

There are some barriers to universal acceptance of this technology and the importance of these varies between different parts of the world: lack of awareness regarding water pollution, little knowledge about the value of human excrement as fertilizer, difficult access to prefabricated components of IESSO and little financing for decentralized sanitation.[2] The existing extensive networks of piped water and sewage may also represent impediments to the adoption of UDDT, since they eliminate two of the factors that drive them and, in addition, represent large public investments. They may restrict efforts to change types of toilets and sanitation.

Another big impediment is that no one wants to handle human excrement. Therefore, it is important to design and promote models that minimize observation, smell and contact with this material during maintenance activities. It is also a reason to organize private or municipal operations for the collection, transportation and treatment of excrement. They could operate similarly to kitchen and garden organic waste collection programs.

It is important that the sanitation system that is selected conforms to the legal framework and that it receives support from the local government.[9]​.

Policies could encourage the extensive use of IESSO through financial support of research programs, regulations requiring resource recovery from wastewater, and strict compliance with standards that control environmental pollution.[9]​.

Number of users

Although there are no exact figures, the German Development Cooperation Agency (GIZ) has estimated, in 2012, that there are about 2 million IESSO users, based on known projects in 84 countries.

Regulations

The International Association of Plumbing and Mechanical Officials (IAPMO) has recently proposed an addendum to its Green Plumbing Code, which “indicates performance criteria for mass-produced or site-built composting toilets, with or without urine separation.”[34] If approved, it will appear in the 2015 edition of the Green Supplement to the Uniform Plumbing Code.

Several North American states allow the disposal of feces from IESSO or composting toilets (generally, they do not distinguish between dry toilet types) by burying them under at least 6 inches of soil. For example:.

For dry toilet users in the United States (including those using IESSO), it is important to remember that while it does not refer to this material as “fertilizer,” but simply a disposable material, Federal Rule 503 (called the “EPA Sludge Rule”) has no jurisdiction over dry toilet products and all control of these materials rests with individual states.[39]​.

Currently, the use of urine as fertilizer in the US is still in its infancy. The NGO Rich Earth Institute (richearhinstitute.org) is demonstrating its feasibility in Brattleboro, Vermont. So far, there do not appear to be regulations specifically regarding urine use in the US, but as urine-separating toilets become more common, they need to be formulated.